Solar UV-B radiation affects below-ground parameters in a fen ecosystem in Tierra del Fuego, Argentina: implications of stratospheric ozone depletion

Authors

  • Johann G. Zaller,

    Corresponding author
    1. The Ecology Center, Utah State University, 5205 Old Main Hill, Logan, Utah 84322–5205, USA.,
      Johann G Zaller, Institute of Organic Agriculture, University of Bonn, Katzenburgweg 3, D-53115 Bonn, Germany. fax + 49 (228) 73 56 17, e-mail: jzaller@uni-bonn.de
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  • Martyn M. Caldwell,

    1. The Ecology Center, Utah State University, 5205 Old Main Hill, Logan, Utah 84322–5205, USA.,
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  • Stephan D. Flint,

    1. The Ecology Center, Utah State University, 5205 Old Main Hill, Logan, Utah 84322–5205, USA.,
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  • Ana L Scopel,

    1. IFEVA, Consejo Nacional de Investigaciones Científicas y Técnicas, and Universidad de Buenos Aires, Avenida. San Martín 4453, 1417 Buenos Aires, Argentina
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  • Osvaldo E. Salo,

    1. IFEVA, Consejo Nacional de Investigaciones Científicas y Técnicas, and Universidad de Buenos Aires, Avenida. San Martín 4453, 1417 Buenos Aires, Argentina
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  • Carlos L. Ballaré

    1. IFEVA, Consejo Nacional de Investigaciones Científicas y Técnicas, and Universidad de Buenos Aires, Avenida. San Martín 4453, 1417 Buenos Aires, Argentina
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Johann G Zaller, Institute of Organic Agriculture, University of Bonn, Katzenburgweg 3, D-53115 Bonn, Germany. fax + 49 (228) 73 56 17, e-mail: jzaller@uni-bonn.de

Abstract

Stratospheric ozone depletion caused by the release of chlorofluorocarbons is most pronounced at high latitudes, especially in the Southern Hemisphere (including the so-called ‘ozone hole’). The consequent increase in solar ultraviolet-B radiation (UV-B, 280–315 nm) reaching the earth's surface may cause a variety of alterations in terrestrial ecosystems. Most effects might be expected to occur above-ground since sunlight does not penetrate effectively below-ground. Here, we demonstrate that solar UV-B radiation in a fen in Tierra del Fuego (Argentina), where the ozone hole passes overhead several times during the Austral spring, is causing large changes of below-ground processes of this ecosystem. During the third and fourth year of a manipulative field experiment, we investigated root systems in these plots and found that when the ambient solar UV-B radiation was substantially reduced, there was a 30% increase in summer root length production and as much as a threefold decrease in already low symbiotic mycorrhizal colonization frequency of the roots compared with plots receiving near-ambient solar UV-B. There was also an apparent shift toward older age classes of roots under reduced solar UV-B. Such large changes in root system behaviour may have decided effects on competition and other ecological interactions in this ecosystem.

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